1. Field of the Invention
The invention relates to energy-absorbing shock cells for mounting bumpers, barriers, or like devices or angularly extending or slanting legs of fixed offshore oil rig structures, such as platforms, barge loading docks, or similar structures.
More particularly the invention relates to shock cells having anti-pull-out components which prevent the shock cells from being pulled or torn apart or destroyed. Such pull-out shock cell failure can occur when a ship becomes trapped, tied or otherwise engaged to or with bumpers or barriers mounted by such shock cells on a fixed oil rig structure, and when such ship moves relative to the rig structure, for example by wave action. Such shock cell failure can require complete rebuilding of the bumper or barrier and replacement of the damaged shock cell or cells.
2. Description of the Prior Art
Prior shock cells are known wherein inward telescoping of the cell inner cylinder is stopped or cushioned by a stop member, which may shatter, in the cell outer cylinder when a bumper or barrier on an oil rig is rammed by or acts to fend off a boat or barge striking the bumper or barrier with great force, as in U.S. Pat. No. 4,109,474. However, such prior devices do not protect the rig structure from pull-out shock cell failure damage.
When a ship is tied to a dock bumper, wave action or wind may react against the ship to move the ship away from the dock. Sometimes such pull-away forces become strong enough that the shock cell at top or bottom of a bumper will pull the inner shock cell cylinder completely out of a shock cell mounting.
A similar failure can occur when a ship accidentally pulls away from a rig structure while still tied to a rig barrier mounted by shock cells on the rig structure.
Accordingly, there has been a long-felt want and there is an existing need for an anti-pull-out shock cell structure for mounting bumpers or barriers on fixed offshore oil rigs which will avoid the extensive damage to and the costly repairs required for oil rigs which previously have resulted when a shock cell pull-out incident has occurred.